Chapter 20 Air Pollution. Overview of Chapter 20  Atmosphere as a Resource  Types and Sources of Air Pollution  Effects of Air Pollution  Controlling

Download Chapter 20 Air Pollution. Overview of Chapter 20  Atmosphere as a Resource  Types and Sources of Air Pollution  Effects of Air Pollution  Controlling

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  • Chapter 20Air Pollution

  • Overview of Chapter 20Atmosphere as a ResourceTypes and Sources of Air PollutionEffects of Air PollutionControlling Air Pollution in the USOzone Depletion in the StratosphereAcid DepositionAir Pollution Around the WorldIndoor Air Pollution

  • Atmosphere as a ResourceAtmospheric CompositionNitrogen: 78.08%Oxygen: 20.95%Argon: 0.93%Carbon dioxide: 0.04%Ecosystem servicesBlocks UV radiationModerates the climateRedistributes water in the hydrologic cycle

  • Air Pollution - TerminologyAir PollutionChemicals added to the atmosphere by natural events or human activities in high enough concentrations to be harmful Two categoriesPrimary Air PollutantHarmful substance that is emitted directly into the atmosphere Secondary Air PollutantHarmful substance formed in the atmosphere when a primary air pollutant reacts with substances normally found in the atmosphere or with other air pollutants, or with sunlight

  • Major Air Pollutants

  • Major Classes of Air PollutantsParticulate MaterialNitrogen OxidesSulfur OxidesCarbon OxidesHydrocarbonsOzone

  • Particulate MaterialThousands of different solid or liquid particles suspended in airIncludes: soil particles, soot, lead, asbestos, sea salt, and sulfuric acid droplets DangerousMay contain materials with toxic/carcinogenic effectsSmall particles can become lodged in lungs

  • Nitrogen and Sulfur OxidesNitrogen OxidesGases produced by the chemical interactions between atmospheric nitrogen and oxygen at high temperatureGreenhouse gases that cause difficulty breathingSulfur OxidesGases produced by the chemical interactions between sulfur and oxygen Causes acid precipitation

  • Carbon Oxides and HydrocarbonsCarbon OxidesGases carbon monoxide (CO) and carbon dioxide (CO2) Greenhouse gasesHydrocarbonsDiverse group of organic compounds that contain only hydrogen and carbon (ex: CH4- methane)Some are related to photochemical smog and greenhouse gases

  • OzoneTropospheric OzoneMan- made pollutant in the lower atmosphereSecondary air pollutantComponent of photochemical smogStratospheric OzoneEssential component that screens out UV radiation in the upper atmosphereMan-made pollutants (ex: CFCs) can destroy it

  • Sources of Outdoor Air PollutionTwo main sourcesTransportationIndustryIntentional forest fires is also high

  • Urban Air PollutionPhotochemical Smog (ex: Los Angeles below)Brownish-orange haze formed by chemical reactions involving sunlight, nitrogen oxide, and hydrocarbons

  • Formation of Photochemical Smog

  • Sources of Smog in Los Angeles

  • Effects of Air PollutionLow level exposureIrritates eyesCauses inflammation of respiratory tractCan develop into chronic respiratory diseases

  • Children and Air PollutionGreater health threat to children than adultsAir pollution can restrict lung developmentChildren breath more often than adultsChildren who live in high ozone areas are more likely to develop asthma

  • Without Electrostatic precipitatorWith Electrostatic precipitator Controlling Air Pollution Smokestacks with electrostatic precipitator (right)

  • Controlling Air PollutionSmokestacks with scrubbers (right)Particulate material can also be controlled by proper excavating techniques

  • Controlling Air PollutionGasoline vapors are a major source of VOCs (volatile organic compounds), which are extremely harmful!Phase I Vapor Recovery System for gasoline involves collecting unburned vapors from underground tanks at gas stations!

  • The Clean Air ActAuthorizes EPA to set limits on amount of specific air pollutants permittedFocuses on 6 pollutants:lead, particulate matter, sulfur dioxide, carbon monoxide, nitrogen oxides, and ozoneAct has led to decreases

  • The Clean Air Act

  • Urban Air Quality

  • Other Ways to Improve Air QualityReduce sulfur content in gasoline from its current average of 330 ppm to 30 ppmSulfur clogs catalytic convertersRequire federal emission standards for all passenger vehiclesIncluding SUVs, trucks and minivansRequire emission testing for all vehiclesIncluding diesel

  • Ozone Depletion in StratosphereOzone Protects earth from UV radiation

  • Stratospheric Ozone:Ozone (O3) forms a layer in the stratosphere, measured in Dobson Units (typically 260 DU near the equator, higher toward the poles)Ozone is created when UV radiation strikes molecules of Oxygen (O2) in the stratosphere, and splits (dissociates) them into free O atoms, which then quickly combine to form ozone.O2 + UV -> O + OO + O2 -> O3

  • Stratospheric Ozone:Ozone can then be destroyed & reformed by the same UV radiation, in a natural cycle as follows:O3 + UV -> O2 + O O + O2 -> O3 as aboveOzone levels peak at about 25 KM above Earths surface.Stratospheric Ozone absorbs 99% of UV if left at natural levels

  • Three Categories of UV Radiation:

  • Ozone Depletion in StratosphereOzone thinning/holeFirst identified in 1985 over AntarcticaCaused by human-produced bromine and chlorine containing chemicals. (Halogens)Ex: CFCspropellants used for aerosol cans (no longer in use)coolants in refrigeration (Freon)foam (Styrofoam) blowing agents in insulationsolvents

  • How does Chlorine (CFC) destroy Ozone?Chemical reaction creates a catalyst!CCl3F + UV Cl + CCl2FCl + O3 ClO + O2ClO + O Cl + O2

  • Ozone Depletion in StratosphereHole over Antarctica requires three conditions:The development of the circumpolar vortex - a mass of frigid air that circulates around the southern polar region The formation of polar stratospheric clouds masses of ice crystals onto which Cl and Br can settle. This enables Cl and Br to destroy ozoneSunlight just returning to polar region (occurs in spring in the S. hemisphere (Sept. Oct.) which triggers the release of the Cl and Br from the polar stratospheric clouds

  • Effects of Ozone DepletionHigher levels of UV-radiation hitting the earthEye cataractsSkin cancer (right)Weakened immunityMay disrupt ecosystemsMay damage crops and forests

  • Recovery of Ozone LayerMontreal Protocol (1987)Reduction of CFCsStarted using HCFCs (greenhouse gas)Phase out of all ozone destroying chemicals is underway globallySatellite pictures in 2000 indicated that ozone layer was recoveringFull recovery will not occur until 2050

  • Acid DepositionSulfur dioxide and nitrogen dioxide emissions react with water vapor in the atmosphere and form acids that return to the surface as either dry or wet deposition pH scale

  • How Acid Deposition Develops

  • Effects of Acid DepositionDeclining Aquatic Animal PopulationsThin-shelled eggs prevent bird reproductionCalcium is unavailable in acidic soilForest decline

  • Acid Deposition and Forest Decline

  • Air Pollution Around the WorldAir quality is deteriorating rapidly in developing countries Developing countries have older carsShenyang, ChinaResidents only see sunlight a few weeks each year5 worst cities in worldBeijing, China; Mexico City, Mexico; Shanghai, China; Tehran, Iran;Calcutta, India

  • Case-In-Point Air Pollution in Beijing and Mexico CityBeijing (left)Mexico City (above)

  • Global Distillation Effect Long Distance Transport of Air Pollutants

  • Indoor Air PollutionPollutants can be 5-100X greater than outdoorsRadon, cigarette smoke, carbon monoxide, nitrogen dioxide, formaldehyde pesticides, lead, cleaning solvents, ozone, and asbestos

  • Indoor Air Pollution - Radon



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